Mixing devices for mixing a pulverulent polymer and a liquid monomer for the manufacture of bone cement are previously known from U.S. Pat. No. 5,328,262 and U.S. Pat. No. 5,551,778. In the embodiment of U.S. Pat. No. 5,551,778, the liquid substance—here a monomer—is located in a closed container. This container is placed in a mixing chamber in which a pulverulent substance—here a polymer—is also located. The container with the liquid substance is opened by penetrating the wall thereof, whereby the liquid and pulverulent substances come in contact with each other and may be mixed with each other.